This invention relates generally to coin operated telephones, and more particularly, to coin operated telephones having self-contained control circuitry.
Coin operated telephones are typically of the type that have a central office controlling the operation of the coin operated telephone. When a user wishes to use this type of telephone, the user deposits a minimum amount (typically 10 cents), dials a telephone number of a called party, and a central office enables completion of the call once the minimum cost of the call has been satisfied, determines how much that call will cost beyond the minimum amount already deposited, and advises the caller of any added cost to allow continuation of that call. When the called party answers, the user can immediately speak with the called party. The minimum cost coins and additionally deposited coins are collected, or returned, under the control of the central office. For example, if the called party does not answer, or if the called telephone is busy, the deposited coins are returned. Signals from the central office which enable collection or return of deposited coins are not provided on all telephone lines emanating from a central office, but are provided typically to only those telephone lines running from the central office to central office owned coin operated pay phones. With telephone rate deregulation it is now permissible in many areas to have private ownership of coin operated telephones. Thus, one may purchase his or her own coin operated telephone, install it in his or her own place of business, as a restaurant, for example, and connect it to the conventional telephone line running into such place of business. Such purchased pay phones have self-contained control and thus have means, internal to the telephone, to compute required coin deposits and to control whether deposited coins should be collected or returned. In one such self-contained pay phone, the coin operated telephone is initially coupled to the central office when the user removes a handset from a switchhook so that a dial tone may be supplied from the central office to prompt the user to enter the telephone number of a called party. Once digits of the telephone number are entered, the phone is decoupled from the central office and the telephone number entered is stored in the telephone. The minimum charge for the call is calculated by means within the telephone and once the user satisfies that charge by depositing coins, the connection to the central office is reestablished by control circuitry within the phone. Then the stored telephone number is dialed by the circuitry within the phone to the central office. When the called party answers, deposited coins are retained, otherwise, they are returned. Detection of the answering by the called party can be accomplished electrically by detecting a momentary reversal in the voltage generated by the central office (a so-called "line reversal" ), but momentary line reversal is not provided by all central offices, so in one known telephone of this type, the user is required to activate a switch when he or she hears the voice of the called party and activation of the switch enables coin collection. That is, if such switch is not activated and the called party answers, the user's audio transmission is muted so that the called party is unable to hear the voice of the user. Thus, for the called party to hear the caller, the switch must be activated and it is the activation of the switch which causes, ultimately, the collection of the deposited coins. If, however, the switch has not been actuated by the time the user replaces the handset onto the switchhook, as when the called party does not answer, or if the called telephone is busy, the coins are returned. In either case, a central office is still required at the initiation of the call to provide a local dial tone to prompt the caller to enter the desired telephone number and this requires a coupling of the phone to the central office. Hence, the central office is used twice, once to just provide a dial tone and another to complete the call.
In a private branch exchange (PBX), there is provided a local dial tone generator, located within the PBX, to prompt telephone number of a called party or an access code to couple the user's telephone to a central office. All control over the operation of the telephone coupled to the PBX is controlled by that PBX and not by circuitry disposed internally to the telephone. Further, PBX's are not designed to couple to coin operated telephones. Therefore, conventional coin operated telephones as described above are not generally coupled to a PBX.
Another problem with self-contained pay phones is that it is generally desirable to prevent the user (typically a patron in the telephone owner's place of business) from accepting collect calls which will in effect be charged to the owner of the phone. Two approaches are generally used: restricting indication of incoming calls by circuitry within the phone; or, by alerting an operator that the accepting party (the patron/user) is accepting the call from a coin operated telephone. Restricting indication of incoming calls has been generally limited to disabling an indicator (i.e., the ringer) in the phone to prevent the user of the coin operated telephone from knowing that a call is incoming; however, the user can circumvent this feature by coordinating with a caller the time at which the caller will call so that at the appropriate pre-arranged time the user will remove the handset from the coin operated telephone, answer the call, and accept the "reverse" or collect charges. Some coin operated telephones include circuitry which attempts to alert an operator (if it is a collect call) that the answering telephone is a coin operated telephone and no charges are to be accepted by the telephone transmitting a short tone to the operator. If the operator should miss hearing the tone burst or not know what the tone means, the operator could allow the call. Obviously, neither approach provides a positive method of preventing incoming calls from being charged to the owner of the phone.